Method and apparatus for drying liquid deposited on liquid receptive material

ABSTRACT

An electronic dryer for setting ink comprising spaced electrodes of an antenna radiating a high potential radiofrequency electromagnetic field through which is passed a liquid receptive material, such as paper, having wet ink thereon. A shield of dielectric material is positioned to extend between the electrodes to prevent arcing between the electrodes. In addition, ionized air around the electrodes is removed to further minimize the possibility of interelectrode arcing. A static electricity eliminator is employed to generate an electromagnetic field for removing static charges from the paper to prevent arcing between the paper and the electrodes.

United States Patent Keith METHOD AND APPARATUS FOR DRYING LIQUIDDEPOSITED ON LIQUID RECEPTIVE MATERIAL Appl. No.: 35,146

Related U.S. Application Data Continuation-in-part of Ser. No. 1,030,Jan. 6, i970, abandoned.

U.S. Cl ..34/l, 2l9/l0.8l Int. Cl ..B0lk 5/00 Field of Search ..34/l;2l9/l0.8l

[ 51 Jan. 25, 1972 [56] References Cited UNITED STATES PATENTS 3,491,4571/1970 Schreiber et al ..34/l 3,532,848 10/1970 Loring, Jr. et al. ..2l9/l0.8l

Primary Examiner-Charles Sukalo Attorney-Richards, Harris & Hubbard [57]ABSTRACT An electronic dryer for setting ink comprising spacedelectrodes of an antenna radiating a high potential radiofrequencyelectromagnetic field through which is passed a liquid receptivematerial, such as paper, having wet ink thereon. A shield of dielectricmaterial is positioned to extend between the electrodes to preventarcing between the electrodes. In addition, ionized air around theelectrodes is removed to further minimize the possibility ofinterelectrode arcing. A static electricity eliminator is employed togenerate an electromagnetic field for removing static charges from thepaper to prevent arcing between the paper and the electrodes.

28 Claims, 32 Drawing Figures alsssl-sa'r PATENTED JAN25 i872 sum 01 grw FIG. I

v Q a 4 FIG. 2

PATENTEU M25 I972 SHEET 030? 10 FIG. 6

FIG. 5

rATemmJms-m alsasssv INVENTOR:

CHARLES N. KEITH Z'M, mf'zwu ATTORNEYS Pmmmmzsm 3636.637

SHEET [)8 HF 10 lNVENTOR:

CHARLES N. KEITH 332 FIG. 30 QM ATTORNEYS PATENIEDJANZSBYZ SHEET UQUF 10FIG. 22

METHOD AND APPARATUS FOR DRYING LIQUID DEPOSITED ON LIQUID RECEPTIVEMATERIAL This is a continuation-in-part application of an applicationfiled Jan. 6, 1970, Ser. No. L030, now abandoned.

This invention relates to electronic drying, and more particularly toelectronic drying of a liquid on a liquid receptive material by aradiofrequency electromagnetic field. A major problem which has alwaysbeen present in the printing industry is the offsetting or smudging ofwet ink onto the back of printed sheets of paper when they are stackedin the delivery.

station of a printing press.

Two basic types of antioffset devices are presently being utilized bythe printing industry. The most common type of antioffset device, usedwith sheet-fed printing presses, employs spray powder applied betweenindividual sheets, to separate the sheets, to prevent offsetting of wetink from the face of one sheet to the back of another sheet by holdingthe sheets in spaced-apart relation until the ink dries. Natural dryingof the ink may require several hours, which results in wasted timebefore sheets can be run through the press for printing on the back ofthe sheets or for multicolor printing on the same side of the sheet. Thespray powder is a direct result of an appreciable portion of thedowntime of a printing press because powder adheres to the blanketcylinder which must be cleaned often. On long runs the powder istransferred into the ink train which must be cleaned. Powder isdetrimental to the press and adjacent machinery as well as a healthhazard.

Large gas-fired heating ovens are the most common type of antioffsetdevice for use with web presses. Ovens are normally very inefiicient andexpensive to purchase and install and require an excessive amount ofspace in the printing shop. Solvents are flashed off and dissipated intothe air or must be vented through elaborate systems. After paper hasbeen run through an oven, refrigerated rollers are employed to bring thepaper and ink back to room temperature. The ovens, often operating attemperatures as high as 600 F., remove an undesirable amount of moisturefrom the paper which makes the paper brittle, unstable and causescracking of the paper in folding and converting operations.

Many different ink compositions have been developed in an effort toprovide quick-drying ink to compensate for these problems. varnishes,pigments, solvents, waxes, dyes and driers constitute the major elementsof the various compositions of ink. Drying is accomplished primarily bythe absorption of the solvents into the paper and the addition of dryersto the ink.

Heretofore attempts have been made to employ highfrequency electricalpower to dry ink. However, no electronic dryer heretofore developed hashad the capability of generating a useable electric field at asufficiently high potential, and at optimum frequency, to effectivelyand economically dry ink in the time limits required in pressoperations. The long felt but unsolved need for efficient and economicaldrying apparatus has resulted in excessive printing costs for less thanoptimum quality.

This invention relates to an electronic dryer which has the capabilityof drying ink on a printed sheet or web. A high potential radiofrequencyfield, through which the paper is passed, causes slight dielectricheating of the paper. However, the temperature of the paper is notraised appreciably as it is passed adjacent the dryer and the moisturecontent of the paper is only slightly reduced.

It is believed that the outermost electrons of certain elements inmolecules comprising the ink composition, while having high energy, areloosely bound to their nucleus and perhaps are being shared by othermolecules because of their distance from the nucleus and also because ofthe shielding effect of the innermost electrons. As wet ink is movedthrough high energy electromagnetic radiation, molecular redistributionof the components of the ink results. Detachment of some of theoutermost electrons in the molecules comprising the ink is thought toresult in a certain amount of electromagnetically induced ionization.This is believed to cause a molecular rearrangement producing molecularattachments of very high viscosity thereby setting the ink very quickly.

It should be appreciated that, while the detailed description of thepreferred embodiment of the invention relates primarily to the drying ofink on paper, the invention has applications for treating materialsother than paper and effectively acts upon liquids other than ink.

The term liquid receptive" as used herein means having an affinity forliquid such that liquid is attracted to the receptive material whichcauses atoms of the liquid to enter into or remain on the surface of thematerial. The term dry as used herein includes, not only, reduction inmoisture, but also, changing from a soft wet state to a relatively solidstate by subjectingliquid to electromagnetic energy to form a newinternal molecular structure causing the liquid to set or cure. Thedrying apparatus described herein may be positioned at locations otherthan at the delivery station of a press. For example, positioning thedryer between printing stations in a multicolor press allows drytrapping wherein one color of ink is printed over another color.

The invention comprises spaced electrodes for producing a shaped, highpotential field of radiofrequency electricity. The shape of theelectrodes and the spacing therebetween controls the shape of the field.

A shield of dielectric material having a low dissipation factor and highbreakdown voltage, such as Teflon (tetrafluoroethylene polymer,) orsilicone rubber, is shaped and positioned to prevent ionization of theair in sufficient magnitude to form a conductive path, thus preventingarcing between the electrodes.

A static eliminator is incorporated into the device for removingstaticelectric charges from the material being dried, which result froma number of contacts with dissimilar objects while moving through thepress during the printing operation. The static charge is removed bypassing the material through an alternating electromagnetic field,leaving the material substantially static charge free. This preventssubsequent arcing between the high potential electrodes and thematerial.

An object of the present invention is to provide a method and means ofquickly drying ink while occupying a minimum amount of space, andwithout undesirable side effects, which result in downtime of theprinting press, in high maintenance costs, substantial reduction in themoisture content of the paper, and reduction of printing quality.

A further object of the invention is to provide a drying device ofsimple inexpensive construction capable of producing a high potentialelectromagnetic field positioned so that paper may be moved therethroughwithout arcing between electrodes.

A further object of the invention is to provide a drying device ofsimple inexpensive construction capable of producing a high potentialelectromagneticfield positioned so that paper may be moved therethroughwithout arcing between electrodes.

A further object of the invention is to provide an electronic dryingdevice having a static eliminator for removing static electricity frompaper as it is passed adjacent thereto.

A still further object of the invention is to provide an electronicdrying device which may be readily adapted to sheetfed or web-fedlithographic printing presses.

A still further object of the invention is to provide an electronicdrying device which produces a high potential radiofrequencyelectromagnetic field providing high efficiency for drying ink withminimum input power.

A still further object of the invention is to provide an electronicdrying device generating an electromagnetic field which is designed toprevent propogation of radio waves outside of the unit.

A still further object of the invention is to provide a method of dryingink comprising the elimination of static charges, and shaping andconcentrating electromagnetic energy to efficiently operate primarily onthe ink.

Other and further objects of the invention will become apparent from thefollowing description and drawings annexed hereto.

Drawings of suitable embodiments of the invention are annexed hereto sothat the invention may be better and more fully understood, in which:

FIG. 1 is a side elevational view of the delivery station of a sheet-fedprinting press with the dryer embodying the present invention mountedtherein;

FIG. 2 is a cross-sectional view taken substantially along line 2-2 ofFIG. 1 and FIG. 3;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 3;

FIG. 7 is a cross'sectional view taken along line 7-7 of FIG. 3;

FIG. 8 is a schematic wiring diagram of the electrical circuit;

FIG. 9 is an enlarged cross-sectional view taken along line 9-9 of FIG.6;

FIG. 10 is an enlarged cross-sectional view of an electrode;

FIG. 11 is a fragmentary perspective view of an end portion and mountingof an electrode;

FIG. 12 is a fragmentary cross-sectional view taken along line 12-12ofFIG. 9;

FIG. 13 is a cross-sectional view of a second embodiment of the dryertaken along line 13-13 of FIG. 14;

FIG. 14 is a cross-sectional view taken along line 14-14 of FIG. 13;

FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 14;

FIG. 16 is an enlarged cross-sectional view taken along line 16-16 ofFIG. 13;

FIG. 17 is a schematic view of a modified form of the inventron;

FIG. 18 is a cross-sectional view taken along line 18-18 of FIG. 17;

FIG. 19 is a schematic view of another modified form of the invention;

FIG. 20 is a schematic view of another modified form of the invention;

FIG. 21 is a fragmentary schematic view of another modified form of theinvention;

FIG. 22 is a sectional view showing the rear of an antenna employingcircular radiating electrodes;

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. l and 2 of thedrawing, the numeral 1 generally designates a housing which contains thecomponent parts of the oscillator section of a dryer including aradiating head or antenna 2 which comprises means for producing a shapedhigh-frequency, high potential electromagnetic field. Wet,liquid-receptive material, such as printed sheets of paper 4, are movedthrough the delivery station 12 by gripper bars 6, which are carried byan endless chain 8 on chain rails 10, mounted on the delivery station12. Sheets 4 are transferred to the delivery station and deposited in astack 16 after passing through one or more printing stations 14.

Chain rails 10 are grounded by a suitable conductor of highfrequencyelectricity 3a and the rails 10 are preferably constructed of a highlyconductive material, such as brass, to maintain gripper bars 6 atsubstantially ground potential.

Electrical power, regulated through control station 22, is delivered tothe inside of housing 1 through a conductor 18 connected to aconventional direct current power supply 20. Conductor 24 interconnectsa conventional source of alternating current (not shown) and powersupply 20. A suitable cooling system 26 may be used in conjunction withdirect current power supply 20 and oscillator section 1 if it is deemednecessary to do so. An arc suppressor 21 (FIG. 8) is associated with thecontrol station 22 as will be hereinafter more fully explained.

Control station 22 (FIG. 8) comprises suitable electrical components foradjusting the output of power supply 20. Station 22 has start and stopswitches 22a and 22b, plate voltage indicator 22c, plate currentindicator 22d, grid current indicator 222, and control 22f connected toa potentiometer for regulating the output power of supply 20. Electricalconduit 22!: contains suitable conductors for connecting control station22 to the power supply 20.

As best illustrated in FIGS. 3, 4 and 8, an electronic tube, such astriode 30, is mounted in an oscillator circuit 32 enclosed in housing 1.Triode 30 is a conventional electrical component well known to thosehaving ordinary skill in the art. Suitable means, such as blower 30a, isprovided for cool ing triode 30.

The cathode or filament 300 of triode tube 30 is connected throughconductors 31 and 33 to a transformer 34 which is connected throughconductors 36 and 37 to power supply (not shown).

FIG. 23 is a cross-sectional view taken along the line 23-23 of FIG. 22;7

FIG. 24 is a cross-sectional view taken along the line 24-24 of FIG. 22;

FIG. 25 is an enlarged cross-sectional view of three electrodes of theantenna of FIG. 22;

FIG. 26 is a fragmentary perspective view of an end portion and mountingof a circular electrode;

FIG. 27 is a fragmentary cross-sectional view taken along line 27-27ofFIG. 25;

FIG. 28 is a section of a portion of an electronic dryer taken along theline 28-28 of FIG. 29 where the liquid receptive material passes betweenopposing set of electrodes;

FIG. 28a is a sectional view taken along the line 28a28a of FIG. 29ashowing a modification of the antenna of FIG. 28;

FIG. 29 is a sectional view taken along the line 29-29 of FIG. 28;

FIG. 29a is a sectional view taken along the line 29a-29a of FIG. 28;and

FIG. 30 is an enlarged cross-sectional view of a portion of the antennaof FIG. 29.

Numeral references are employed to designate like parts throughout thevarious figures of the drawing.

Plate terminal 30p of triode 30 is connected through conductor 38 to avariable capacitor 39 in series with a variable inductance 42 which isconnected through conductor 40 to mounting bar 42 as will be hereinaftermore fully explained.

The grid terminal 30g of triode 30 is connected through conductor 44 tovariable capacitor 46 which in turn is connected through conductor 47 tocoil 48. Coil 48 is connected through conductor 50 to conductor 38 atnode 37, to capacitor 39 and conductor 40 to mounting bar 42.

The triode 30 and the interconnection to the capacitor 46 and the coil48 comprise an oscillator circuit. This circuit oscillates at afrequency determined by the capacitor 46 and the coil 48 and may beadjusted by means of the capacitor. In operation with the antenna 2, theoscillator continues to operate at the predetermined frequency, sincethe antenna does not appreciably load the circuit. To minimize the loadeffect by the antenna, the capacitor 39 and the inductor 42 are adjustedfor the material being passed through the electromagnetic field of theantenna.

It should be noted that conductors 38, 40, 44, 47, and 50 are very shortto minimize losses in the electrical circuit.

The remote control station 22 comprises a circuit for controlling thecurrent and voltage to the oscillator circuit 32. Since this isconsidered to be a conventional circuit, further discussion thereof isnot deemed necessary.

A conventional arc suppressor 21 is electrically connected to theoscillator circuit 32 to anticipate and prevent arcing betweenelectrodes 56 and 58. The are suppressor is a means to detect anincrease in the power consumed at the antenna 2 of the dryer. As an arcbegins to form between electrodes 56 and 58, the suppressor 21 detectsthe formation of the arc and momentarily interrupts the power suppliedto the oscillator circuit. The function of the arc suppressor is toprevent damage to the material being dried and to the electrodes.

In the embodiment of the invention illustrated in FIGS. 1-12, mountingbars 42 and 52, 42a and 52a, and 42b and 52b have upper and lower endsattached through standofi insulators 54 to the top 1a and the bottom lbof housing 1. These mounting bars are disposed in spaced-apart relationwith the mounting bars 42, 42a and 42b connected to support electrodes56 (see FIG. 4) while mounting bars 52, 52a and 52b are connected to andsupport electrodes 58 (see FIG. 5). A plurality of electrodes 56 isprovided with electrodes 58 being disposed therebetween in spaced-apartparallel relation thereto.

Tank coils 60a and 60b are connected across mounting bars 42a and 52aand tank coils 60c and 60d, across mounting bars 42b and 52b. Thesecoils 60a and 60b are axially aligned and magnetically coupled such thatmutual inductance of each is additive. Two coils 60a and 60b areemployed in parallel to provide low inductance at high voltage.

Mounting bars 52, 52a and 52b, and consequently elec trodes 58, aregrounded at 53g through a conductor 53a and choke coil 53.

While mounting bars 42 and 52 are illustrated as being substantiallystraight conductive members, it should be appreciated that they may becurved such that electrodes 56 and 58 would not lie in a common plane.

From the foregoing it will be apparent that electrodes 56 and 58constitute a capacitive element in the oscillator circuit 32 while tankcoils 60a, 60b, 60c and 60d constitute inductive elements. The dischargeof the capacitive electrodes 56 and 58 through the inductive tank coils60a, 60b 60c and 60d is oscillatory. As explained, since the plateterminal 30p of the triode 30 isconnected through capacitor 46 and thecoil 48 to the grid terminal 30g, the circuit is a free-runningoscillator. The configuration of the electrodes (hereinafter more fullydescribed), the positioning of mounting bars and the particular mannerof mounting the tuning coils all contribute to the provision of anextremely efficient head 2 and the Q or energy-storing effectiveness ofthe oscillator circuit 32 is quite high for an electronic dryingapparatus. The Q of a circuit as illustrated herein ranges from about700 to over 1,000. Since Q is an amplification factor in such a circuit,the high voltage rise at resonance increases the drying efficiency ofthe head 2.

The electromagnetic fields between electrodes 56 and 58 provide energyfor drying ink on the sheet or web of paper or other suitable material 4as the material moves through the fields. Therefore, in one embodimentof the invention, the shape and intensity of the electromagnetic fieldis controlled, as will be explained.

The electric charge on a conductor is. distributed over the surface ofthe conductor and the magnetic field around a cylindrical currentbearing wire is symmetrical about the wire with the strongest part ofthe field being near the wire. The electromagnetic field betweencylindrical conductors is strongest at points along a line extendingbetween the centers of the conductors. To efficiently cause the field tooperate upon ink on a sheet or web, the material should be moved throughthe strongest part of the field.

Provision of an outwardly projecting surface on a conductor results in aconcentration of the electric charge on the curved surface with acorresponding reduction in charge on the surfaces which are not sharplycurved. Concentration of charge may rise to an extremely high value ifthe point is sufficiently sharp.

To this end, electrodes 56 and 58 are somewhat crescent shaped toconcentrate and direct the field outwardly between adjacent bars toallow maximum utilization of the strength of the field without movinggripper bars 6 between electrodes. FIG. 9 illustrates a pair ofconductors 56 and 58 mounted in spaced-apart relation.

Surfaces 57c and 57f (FIG. 10) are preferably symmetrical about axes Aand A which intersect at an angle B which is less than I". The outwardlyconverging convex surfaces 572 and 57f cause electrical charge to movein symmetrically converging paths to the sharply curved points 57. Theconcave front surface 56" extends between and connects the radiatingsurfaces 57f.

Points 57 on the edges of substantially crescent-shaped conductor 56 andpoints 59 on electrode 58 have a radius of curvature r,, for example, ofapproximately 0.03l inches while the radius r, of the convex backportion 56' and 58' of the respective electrodes has a radius ofapproximately 0.21 inches. It should be noted that points 57 havesurfaces which are more sharply curved than any other surfaces on theelectrode 56. Separation between the centers of the bars varies with thestrength of the applied field. It should be understood that thedimensions are merely illustrative and not intended to be limiting innature. However, the specific ratio of r,:r provides good concentrationof charge along points 57 and 59 and the symmetrical configuration andinclination of points 57 and 59 is very efficient for directing thefields in a controlled direction.

It should thus be readily apparent that the crescent-shaped electrodes56 and 58 will direct the electromagnetic field outwardly allowing thesheet4 to be moved therethrough.

At high potentials, the air surrounding a conductor becomes partiallyionized, resulting in brush or corona discharge which represents aleakage of energy. The corona discharge occurs when the potentialgradient exceeds a certain value but is not sufficient to cause arcing.

As best illustrated in FIGS. 4, 5, 11 and I2, opposite ends ofelectrodes 56 and 58 are bent or deflected to form loops 56a and 56b and58a and 58b with the inner ends of the the respective loops beingsecured to mounting bars 42a, 42b, 52a and 52b, respectively, and coils60a, 60b, 60c, and 60d are mounted as hereinbefore described to minimizevoltage built up on the ends of the electrodes. Loops in the end ofelectrodes 56 and 58 reduce the energy which is radiated from the endsof the bars to minimize corona discharge and prevent arcing between theends of the electrodes and between the electrodes and the sides ofhousing 1.

Referring to FIGS. 4, 5 and 11, it should be noted that each electrode56 comprises a straight elongated conductive element 56d which has acurved, substantially U-shaped end portion 56a on one end thereof and acurved end portion 56b on the other end. Points or projections 57constitute elongated conductive surfaces on the electrode 56 to shape ordirect the electromagnetic field between adjacent electrodes.

The substantially crescent-shaped cross section of the straight portionof each electrode feathers out at the ends, as illustrated at 56c (FIG.l1), such that the curved end portions 560 and 56b are substantiallycircular in cross section. Therefore, the end sections 56a and 56b areof circular cross section to minimize the concentration of surfacecharge and curved in a substantially horizontal plane to minimize coronadischarge at the ends of the electrodes.

The inner ends of curved portions 56a and 56b are connected to straightportions 56c and 56f, respectively, which extend inwardly insubstantially parallel spaced-apart relation to sections 56d. Portions56c and 56f join through curved segment 56g with outwardly directedterminal 56h which is adapted to be connected through mounting bars 42to the oscillator 32.

Mounting bars 42, 42a, 42b, 52, 52a and 52b have sockets formed thereinto receive outwardly directed terminals 56h, 58h, respectively. Theterminals on the electrodes are secured in the sockets by setscrews 56jand 58], as best illustrated in FIG. 12.

Electrodes 56 are secured to mounting bar 42 by feed terminals 56! whichextend outwardly from a portion of each electrode 56 intermediate thecurved end portions 56a and 56b thereof. Electrodes 58 are secured tomounting bar 52 by feed terminals 58!.

Positioning terminals 56t and 58: intermediate opposite ends of theelectrodes provides more uniform loading over the area adjacent theantenna 2 thereby resulting in a more balanced electromagnetic fieldacross the antenna at high frequencies than would be achieved if feedterminals were on the ends of the electrodes.

Electrodes 56 and 58 are of substantially identical construction.Referring to FIGS. 4 and 5, it should be apparent that portion 56e ofeach electrode 56 is shorter than portion 56f on the other end of theelectrode while portion 58f of each electrode 58 is shorter than portion58e. This allows spacing of mounting bars without providing electrodesof several different forms and dimensions.

The inner ends of the loops in electrodes 56 terminate adjacent mountingbars 42a and 52b.

The inner ends of loops 58a and 58b are terminated adjacent to mountingbars 52a and 52b.

To keep electrical losses low, electrodes 56 and 58 and the feedersystem must have good conductivity and the insulators 54 must have lowdielectric loss and low surface leakage. The electrodes may beconstructed of copper, aluminum, stainless steel, or other well-knownelectric conductive materials.

As hereinbefore pointed out, the loss in a given length of transmissionline rises with increase in frequency. Therefore, feedlines betweentriode 30 and mounting bar 42 should be kept as short as possible.

The crescent-shaped electrodes may be constructed with sufficient crosssectional area to provide rigidity for the electrodes, therebyminimizing deflection along the length thereof. This further assuresuniformity of the field along the length of the electrodes.

Air is usually a nonconductor of electricity. lts molecules are completein themselves, and neutral, taking no observable part in electricactions so long as they remain neutral.

When an air molecule is exposed to a high potential electromagneticfield, conditions are created in which disturbances occur of sufficientviolence to remove an occasional electron from one of the molecules.When this happens the electron usually attaches itself to a neutralmolecule, thus making it into a negatively charged particle or anegative ion. The molecule which released the electron becomes apositive ion. Ions are thus charged molecules carrying with them aquantity of negative or positive charge which does not balance thecharges of their nuclei.

A great number of ionized molecules can thus be created with the resultthat the air becomes a conductor and neutralizes the charges which werecreating the electric field.

An electric are results from the sudden breakdown of the insulatingstrength of the air or other dielectric material separating twoelectrodes, due to the formation of ions by the intense electric field,accompanied by a rush of electricity through the ionized molecules. Thearcing potential between charged bodies is a substantially linearfunction of the distance between the charged bodies, and for a givendistance the arcing potential is a substantially linear function of thepotential.

The use of crescent-shaped electrodes 56 and 58 for directing andconcentrating the electromagnetic field between the spaced electrodessets up a voltage along points 57 and 59, respectively, which may exceedthe arcing potential of static air insulation therebetween. Thesubstitution of other insulating materials for air increases thepotential gradient which may be held between points 57 and 59 on thespaced elec-' trodes.

The ratio of the capacitance with some material other than air betweenthe plates of a capacitor, to the capacitance of the same capacitor withair insulation, is called the dielectric constant of that particularinsulating material. When a high voltage is applied to conductorsseparated by a dielectric, a considerable force is exerted upon theelectrons and nuclei of the dielectric. Since the dielectric is aninsulator and the electrons do not become detached from their atoms, ifthe force is great enough the dielectric will break down, resulting in apuncture of the dielectric material which will char and permit currentto flow. The breakdown voltage depends upon the com position andthickness of the dielectric material employed.

When conductors on opposite sides of a sheet of dielectric material areoppositely charged a mechanical strain is exerted upon the atoms of thedielectric material. The positively charged particles of the atoms arepulled toward the negatively charged conductor while the negative partsare pulled toward the positively charged conductor. During the extremelyshort time that the atoms of the dielectric material are being realignedor polarized, there is an apparent current flow of electricity due tothe displacement of the charged particles, which is referred to as thedisplacement current. if the electric field is reversed, thedisplacement current occurs for an instant in the opposite direction.

The reorientation of molecules results in heating of the dielectricmaterial by molecular friction, the heat being dissipated to the airadjacent thereto. The power loss due to the dielectric heating is thedielectric loss of the material.

Four primary criteria must be met by a dielectric to functioneffectively to prevent arcing between electrodes 56 and 58. Thedielectric material should have a reasonably high dielectric constant, alow dissipation factor, and a high breakdown voltage so that thematerial will provide good dielectric qualities over a wide range ofoperating frequencies and at high voltage. The dielectric material maybe fonnable or moldable to provide a configuration similar to thatillustrated in FIG. 9 of the drawing.

Since it is necessary that sheet 4, carried by a gripper bar, be movedthrough the electromagnetic field, it is desirable that the electrodes56 and 58 be positioned on the same side of the sheet to allow thegripper bar to pass adjacent thereto. As hereinbefore pointed out, it isdesirable that the field between the electrodes be deflected outwardlyto facilitate moving the sheet therethrough and the dielectric materialmust extend across the field between the electrodes without interferingwith the movement of the sheet 4 through the field.

Experiments reveal that positioning a flat sheet of dielectric materialacross points 57 and 59 of electrodes 56 and 58, respectively, while itdoes increase the voltage differential which can be held between theelectrodes without arcing, additional benefit can be obtained by using ashaped dielectric sheet. The flat sheet, alone, allows the formation ofionized air, which becomes a conductor, allowing an arc to form betweenthe electrodes.

As best illustrated in FIG. 9 of the drawings, shield 70 in a preferredform comprises a sheet of dielectric material having portions draped andextending between electrodes 56 and 58 forming a series of troughs 72which are connected by portions 76 and 78 which extend across points 57of electrode 56 and across points 59 of electrode 58, respectively.Provision of trough portion 72 between electrodes 56 and 58 increasesthe distance which ionized air must travel to form an arc, by

directing the ions rearvvardly around the trough portion 72. it shouldbe noted that shield 70 extends across the electromagnetic field withoutinterference with the movement of sheet 4 through the field and controlsthe distance and direction of travel of the ionized air before it iselectrically connected to an oppositely charged substance. 7

Selection of a material fro construction of sheet 70, which has a lowdissipation factor, is important to minimize dielectric heating of thematerial with resultant changes in molecular structure, and in someinstances melting of the material. Use of material having a lowdissipation factor also minimizes ionization of air from thedisplacement current in the dielectric material, thereby eliminatingarcing and minimizing corona discharge.

Various materials may be employed for constructing shield 70. Teflon, atetrafluoroethylene polymer, has outstanding chemical resistance,excellent electrical properties and good heat stability. Teflon is athermoplastic which may be readily machined or formed and has adielectric constant of approximately 2.1, a dissipation factor of lessthan 0.0002 at one megacycle and a puncture voltage of between 1,000 and2,000

volts per mil (0.00l inch). Teflon is a noncombustible material and hasno true melting point. However, it undergoes a solid-phase transition toa gel at 325 C. with a sharp decrease in strength; and at 400 C. itdecomposes slowly to a gaseous monomer and some gaseous, fluoridederivatives.

Shield 70 may be constructed of materials other than Teflon which have alow dissipation factor, high puncture voltage and good formability. Onesuch material is silicone rubber having a dielectric constant ofapproximately 3.1 and a dissipation factor of 0.0009 at one megacycle.Silicone rubber retains its elasticity at temperatures as high as 300 C.and is unaffected by ozone and corona. Silicone rubber is self-healingsince it does not char if arcing occurs. However, silicone rubber isinferior to Teflon in one respect in that since it has a higherdissipation factor the dielectric heating of a silicone rubber shieldresults in power loss, reducing the efficiency of the dryer.

Housing 1 in which the oscillator circuit and the head 2 are mounted isconstructed of brass, copper, aluminum or other materials which are goodconductors of radiofrequency electricity. The region occupied by head 2is completely enclosed by metal, forming an enclosure which is opaque toelectromagnetic radiation, thus minimizing the propagation of radiowaves into the atmosphere surrounding the housing 1.

Housing 1 is maintained at ground potential by connecting said housingthrough a conductor 3 connected to ground. Delivery station 12 of theprinting press is also maintained at ground potential through groundedconductor 3. Metallic plate 120 of delivery station 12 extendstransversely across the front of head 2 in spaced-apart relationtherefrom and acts as a front for housing 1. Side frames 12b and 12c ofdelivery station 12 extend across the ends of electrodes 56 and 58 inspaced-apart relation therefrom and close the ends of the space betweenplate 12a and the open front of housing 1. The edges 70e of shield 70are secured to the housing 1 and are curved to wrap around the ends 56aand 56b of the electrodes as best illustrated in FIG. 4. The upper andlower edges 70f of the shield are secured to the top and bottom of thehousing 1 as illustrated in FIG. 3.

Housing 1 has openings 1e, if in opposite ends thereof for circulationof air through the housing to cool tube 30. Screens 1s are disposedacross the openings 1e and If to prevent the propagation ofelectromagnetic waves therethrough.

As best illustrated in FIGS. 3, 4, 6 and 7, means comprising a blowermanifold 80 is provided for urging and holding the printed sheet 4 inthe radiated field. Manifold 80 comprises vertically disposed spacedhollow tubular members 82 connected by horizontally disposed spacedhollow tubular members 84 and 85. A suitable source of pressurized air,such as blower 86, is connected to conduit 88 and a suitable coupling 89to the inside of the hollow tubular members. Passages 90 extend throughthe walls of tubular members 82, 84 and 85 such that compressed airpassing through conduit 88 into the hollow portion of the tubularmembers is directed through passages 90 onto the surface of sheet 4,thereby urging the sheet toward electrodes 56 and 58 to maintain thesheet in the outwardly directed field between the electrodes. Manifold80 is held in position by supports 92 secured to the side frames of thedelivery station.

As the sheet 4 is moved through the printing press, static electricityis generated in the sheet. The amount of charge and the polarity of thecharge depends upon many variables such as the type of paper, the typeof ink, press speed, humidity and temperature. If sheet 4 carries a highstatic charge, as it is moved adjacent electrodes 56 and 58, arcing willresult from the sheet to the electrodes, causing severe damage to thesheet making it unuseable.

Means is provided for removing the static charge from sheet 4 before itis moved into close proximity of electrodes 56 and 58 in head 2.

A suitable embodiment of a static eliminator 95 is illus trated in FIGS.7 and 8 of the drawing. Conductors 96 are electrically connected througha conductor 98 to a source of either alternating or direct currentelectricity such as transformer 100. Transformer 100 is connectedthrough conductor 98a to the frame of delivery station 12, which ismaintained at ground potential through conductor 3. Conductor 96 extendthrough hollow portions of tubular members 82, 84 and 85 such that airdirected through .passages in said tubular members is slightly ionizedas a result of corona and is effective to reduce the static charge insheet 4 as it contacts the sheet.

A modified form of a static eliminator is illustrated in FIGS. 17 and 18of the drawing. Conductors 97 and 99 may have a cross section identicalto that of the electrodes 56 and 58 such that an outwardly directedelectromagnetic field will exist therebetween when the electrodes areconnected to conductors 98 and 98a, which are connected to transformer100 as hereinbefore explained. Oppositely charged electrodes 97 and 99produce an electric field therebetween, which is of lower frequency thanthat generated between electrodes 56 and 58, to remove static chargefrom the sheet before the sheet is moved into the higher frequency fieldwhere drying is accomplished.

DESCRIPTION OF A SECOND EMBODIMENT A second embodiment of thearrangement of the electrodes is illustrated in FIGS. 13-16 of thedrawing.

The first embodiment of the invention hereinbefore described andillustrated in FIGS. 1-12 of the drawing may be employed with a webpress for drying ink on a web 104. However, since gripper bars are notemployed for moving the web 104 through the press, electrodes 156 and158 in the modified form may be positioned on opposite sides of the web104.

Electrodes 156 on one side of the web are connected to mounting bar 142which in turn connected to the oscillator circuitthrough conductor 40 ashereinbefore explained with respect to the first embodiment. Electrodes158 are positioned on the opposite side of the web 104 and are supportedby mounting bar 152, which is connected through conductor 153a and chokecoil 1.53 to ground.

Dielectric shields 170a and 17012 are employed to prevent ionization ofthe air which would result in arcing between electrodes 156 and 158.

Tank coils a and 160b are connected to mounting bars 142a and 152a whiletank coils 160a and 160d are connected to mounting bars 142b and l52b.

Electrodes 156 and 158 are slightly difierent configuration fromelectrodes 56 and 58, hereinbefore described. The curved end portions156a and 158u of electrodes 156 and 158 do not extend inwardly towardthe center of each electrode to facilitate attachment of tank coils160a, 160b, 1600 and 160d to mounting bars outwardly of the edges of theweb 104.

The crescent-shaped cross section of the electrodes feather into asubstantially circular cross section as shown at 1560 and 158c.

A third form of a static eliminator is illustrated in FIG. 14 whereinelectrodes 197 and 199 are positioned on opposite sides of the web 104and to conductors 98 and 98a as hereinbefore explained.

Housing 101 extends around radiating heads 102a and has slots 101s inopposite ends thereof through which the web 104 [v passes.

DESCRIPTION OF A THIRD EMBODIMENT As hereinbefore pointed out theprimary function of shield 70 is to prevent completion of a circuit ofionized air which would result in arcing between electrodes 56 and 58.Means other than a shield 70 may be employed to prevent ionization ofthe air in sufficient quantities to prevent arcing between theelectrodes. In the embodiment of the invention illustrated in FIGS. 19and 20 of the drawing, radiating head or antenna 202 comprises spacedelectrodes 256 and 258, positioned across the open side of housing 201.A blower 230a is mounted inside the housing 201 and draws air from theinside of the housing and exhausts air through an opening in the wallthereof.

If a sufficient quantity of air is drawn between the spaced electrodes256 and 258 arcing will not occur across the gap between the electrodes.

While air becomes ionized in the vicinity of each electrode 256 and 258,it is immediately dispersed rearwardly toward blower 230a, preventingformation of an arc which would damage the sheet and electrodes.

A modified form of a third embodiment of the invention is illustrated inFIG. wherein blowers 230b and 2300 are disposed within housing 201 fordrawing air from between electrodes 258' and 256' for use upon a web204.

The form of the invention illustrated and described as the first andsecond embodiments employs shields 70, 170a, 1701: to eliminate arcingas a result of ionization of air adjacent electrodes 56 and 58 byincreasing the distance which the ionized air must travel to form anarc. The third embodiment of the invention illustrated in FIGS. 19 and20 prevents arcing by drawing ionized air from the vicinity of theelectrodes by blower means.

Another modified form is illustrated in FIG. 21 wherein a shield 270 ofdielectric material is positioned as hereinbefore described withrelation to shields 70 and 170.

However, shield 270 has apertures 272 formed therein to form passagesthrough which air may be circulated by blower of the type designated bynumeral 230a in FIG. 19 of the drawing.

DESCRIPTION OF A FOURTH EMBODIMENT Referring to FIGS. 22-27, there isillustrated an embodiment of the invention wherein the antenna radiatingthe radiofrequency electromagnetic field comprises electrodes having acircular cross section. Previous embodiments of the invention haveillustrated the electrodes as having a generally crescent-shaped crosssection. The antenna of this embodiment includes electrodes 300supported on mounting brackets 302 interspersed with electrodes 304supported on mounting bracket 306. One of the mounting brackets 302 isconnected to the oscillator circuit of FIG. 8 through the conductor 40as hereinbefore explained with respect to an earlier embodiment.Mounting brackets 306 are coupled to ground through the choke coil 53.The complete antenna structure is supported in a housing 308 throughstandofi" insulators 310. Wet, liquidreceptive material, such as printedsheets of paper, are moved through an electromagnetic field radiatingfrom the antenna by gripper bars 312 in a manner as explainedpreviously. Interconnecting the mounting brackets 302 and 306 areinductors 314 and 316. Although the inductors are illustrated as onetumcoils, sufficient inductance may be generated to form a tank circuitwith the electrodes 300 and 304 by a straight bar interconnecting themounting brackets. Where required, the inductors 314 and 316 may bewater cooled.

Where required, a static eliminator 318 is positioned from the antennato reduce the static charge on a material transv ported past theradiating antenna. This static eliminator comprises conductors intubular members 320. A similar static eliminator has previously beendescribed.

Referring particularly to FIGS. 25-27, there is shown in detail thecross section of the electrodes 300 and 304 and the supports formounting the mounting brackets. Electrodes 300 are attached to themounting bracket 302 by standoff supports 322 secured to the mountingbracket by a setscrew 324.

Although not specifically illustrated in FIG. 22-27, a dielectric shieldmay be positioned around and between the electrodes 300 and 304 tosubdue arcing between the electrodes caused by ionization of thesurrounding air. Also, as explained previously, the air surrounding theelectrodes 300 and 304 may be displaced by means of a blower. The blowercontinuously replaces the ionized air thereby minimizing the possibilityof arcing between the electrodes.

FIFTH EMBODIMENT OF THE INVENTION Referring to FIGS. 28-30, there isshown an embodiment of the invention wherein electrodes having acircular cross section are mounted such that the liquid-receptivematerial passes between opposed electrode arrangements. The systemsillustrated in FIGS. 28 and 28a both comprise this fifth embodiment withthe electrodes of the system of FIG. 28 on opposite sides of theliquid-receptive maten'al displaced as illustrated in FIG. 29. Indescribing this fifth embodiment, reference numerals followed by aletter identify the system of FIG. 28a.

Electrodes 326 are supported on mounting brackets 328 which are in turnattached to a housing by means of standoff insulators 330. Electrodes326 comprise the upper half of an antenna; the lower half of the antennaincludes electrodes 332. The lower half electrodes 332 are supported onmounting brackets 334 which in turn are attached to the dryer housingthrough standofi insulators 336. As best illustrated in FIG. 29, thelower set of electrodes of the system of FIG. 28 are displaced from theupper half electrodes. The system of FIG. 28 a, as best illustrated inFIG. 29a, has the lower set ofelectrodes in line with the upper set ofelectrodes.

A tank circuit is formed with the upper set of electrodes 326 and thelower set of electrodes 332 by inductors 338 and 340 connected to anupper mounting bar 328 and a lower mounting bar 334. As explainedpreviously, the inductors 338 and 340 may be a straight bar or a barwith a slight curvature, but need not be a coil.

Referring to FIG. 30, there is diagrammatically illustrated anelectromagnetic field between the upper electrodes 326 and the lowerelectrodes 332 for the system of FIG. 28. As the liquid-receptivematerial 342 passes through the electromagnetic field, there will takeplace a drying action of the liquid carried by the material.

In the embodiment of FIGS. 28-30, the individual electrodes of theantenna may be mounted as illustrated in FIGS. 25-27. By interconnectingthe electrodes at several points along their lengths, and in additionrelatively close to the end terminations, a balanced electromagneticfield will be produced. To minimize arcing between the electrodes, ablower may be employed to continuously displace and carry away theionized air as illustrated in FIG. 20.

While several embodiments of the invention, together with modificationsthereof, have been described in detail herein and shown in theaccompanying drawings, it will be evident that various othermodifications are possible without departing from the scope of theinvention.

What is claimed is: 1. In a system for drying a liquid on aliquid-receptive material, comprising:

an antenna positioned along the path of travel of the liquid receptivematerial, said antenna including a first plurality of spaced electrodesand a second plurality of spaced electrodes with individual electrodesof the second group disposed between adjacent electrodes of pairs of thefirst group in the spaced-apart parallel relation thereto,

inductance means connected across said first and second plurality ofelectrodes to form a tank circuit therewith,

generating means having a current output coupled to said antenna,

means for electrically interconnecting the spaced electrodes in groupsto produce a substantially balanced electromagnetic field radiating fromsaid antenna through the liquid receptive material, and

means for direct coupling the groups of spaced electrodes to saidgenerating means in a free-running oscillator configuration.

2. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 including a capacitor in series with an inductanceconnected between said generating means and said antenna.

3. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 including means associated with said antenna to subduearcing between the electrodes.

4. In a system for drying a liquid on a liquid-receptive material as setforth in claim 3 wherein said means to subdue arcing between electrodesincludes a blower for directing ionized air away from said antenna.

5. In a system for drying a liquid on a liquid-receptive material as setforth in claim 3 wherein said means associated with said antenna forsubduing arcing between electrodes comprises a dielectric shieldingmaterial surrounding the spaced electrodes.

6. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 wherein the spaced electrodes of said antenna have acircular cross section.

7. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 wherein the spaced electrodes of said antenna have asubstantially crescent-shaped cross section.

8. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 including means for discharging static electric chargeon the liquid-receptive material positioned along the path of travelthereof.

9. In a system for drying a liquid on a liquid-receptive material as setforth in claim 8 wherein said means associated with said antenna forsubduing arcing between electrodes comprises:

a second plurality of spaced electrodes, and

generating means coupled to said electrodes producing a current outputto generate an electromagnetic field through which the liquid-receptivematerial passes along the path of travel thereof.

10. In a system for drying a liquid on a liquid-receptive material,comprising:

a first plurality of electrodes in spaced-apart relation in an enclosinghousing,

a second plurality of spaced electrodes with individual electrodesthereof disposed between adjacent electrodes of pairs of said firstplurality of electrodes in spaced-apart parallel relation thereto,

inductance means connected across said first and second plurality ofelectrodes to form a tank circuit therewith,

generating means having a current output direct coupled to saidplurality of electrodes in a free-running oscillator configuration toproduce an electromagnetic field radiating therefrom to theliquid-receptive material,

dielectric shielding materials surrounding said electrodes to subduearcing therebetween, and

means for moving the liquid-receptive material through the balancedelectromagnetic field to effect a drying action of the liquid on theliquid-receptive material.

11. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein said means for moving the material throughthe balanced electromagnetic field includes gripper bars having oppositeends thereof movable along chain rails, and

grounded conductors extended along the chain rails to maintain saidgripper bars at a ground potential.

12. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the electrodes have a substantiallycrescent-shaped cross section.

13. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein said electrodes have a substantiallycircular cross section.

14. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the dielectric shielding material has alow dissipation factor.

15. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the dielectric shielding material has ahigh breakdown voltage.

I6. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the dielectric shielding material isformed sheet of tetrafluoroethylene polymer extending across the frontand between the sides of the electrodes in an undulatory path to providetroughs of shielding material between adjacent electrodes.

17. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the electrodes are arranged to form firstand second heads, the first head and second head being disposed onopposite sides of the liquidreceptive material.

18. In a system for drying a liquid on a liquid-receptive material asset forth in claim 10 wherein the housing supporting said electrodes ismaintained at a ground potential and constructed of an electricallyconducted material.

19. In a system for drying a liquid on a liquid-receptive material asset forth in claim 17 including means for urging the liquid-receptivematerial into sliding contact with the dielectric shielding material.

20. In a system for drying ink on a ink-receptive material as thematerial moves through a printing press comprising:

a first plurality of shaped electrodes spaced along and mounted to afirst supporting frame,

a second plurality of electrodes spaced along and mounted to a secondsupporting frame, said second plurality of electrodes having individualelements thereof disposed between adjacent electrodes pairs of saidfirst plurality of electrodes in a spaced-apart parallel relationthereto,

first mounting means for supporting the first plurality of spacedelectrodes on said first supporting frame,

second mounting means for supporting the second plurality of spacedelectrodes on said second supporting frame,

inductance means electrically connected between said first plurality andsaid second plurality of electrodes to form a tank circuit therewith,

means for electrically connecting the first supporting frame to ground,and

generating means having a current output direct coupled to the secondsupporting frame to form a free-running oscillator with said tankcircuit and for producing an electromagnetic field radiating from saidelectrodes through the ink-receptive material.

21. In a system for drying ink on ink-receptive material as set forth inclaim 20 including a static eliminator positioned along the path of thematerial to discharge static charges on the ink-receptive material priorto the material moving through the electromagnetic field produced bysaid first and second plurality of electrodes.

22. In a system for drying ink on an ink-receptive material as set forthin claim 20 including means associated with the electrodes to preventionization of air between electrodes of sufficient magnitude to causearcing therebetween.

23. In a system for drying ink on a ink-receptive material as set forthin claim 22 wherein said means associated with said electrodes toprevent ionization of air includes;:

a housing extending around the electrodes opposite the path of themoving material, and

a blower arranged to direct air through said housing such thationization of air adjacent said electrodes is minimized to preventarcing.

24. In a system for drying ink on an ink-receptive material as set forthin claim 20 wherein said electrodes have a substantially crescent-shapedcross section.

25. In a system for drying ink on an ink-receptive material as set forthin claim 24 wherein the said substantially crescentshaped cross sectionof the electrodes feathers into a substantially circular cross sectionat opposite ends of each electrode.

26. In a system for drying ink on an ink-receptive material as set forthin claim 20 including means mounted in spacedapart relation from theelectrodes for directing the ink-receptive material into the balancedelectromagnetic field.

27. In a system for drying ink on an ink-receptive material as set forthin claim 26 wherein the means for directing material into the balancedelectromagnetic field is a perforated manifold, and

a source of pressurized air communicating with the manifold to directair through the perforation against the material.

28. In a system for drying ink on an ink-receptive material as set forthin claim wherein the electrodes of said first and 5 second plurality arearranged to form first and second heads, the first head and second headbeing disposed on opposite sides of the ink-receptive material.

2. In a system for drying a liquid on a liquid-receptive material as setforth in claim 1 including a capacitor in series with an inductanceconnected between said generating means and said antenna.
 3. In a systemfor drying a liquid on a liquid-receptive material as set forth in claim1 including means associated with said antenna to subdue arcing betweenthe electrodes.
 4. In a system for drying a liquid on a liquid-receptivematerial as set forth in claim 3 wherein said means to subdue arcingbetween electrodes includes a blower for directing ionized air away fromsaid antenna.
 5. In a system for drying a liquid on a liquid-receptivematerial as set forth in claim 3 wherein said means associated with saidantenna for subduing arcing between electrodes comprises a dielectricshielding material surrounding the spaced electrodes.
 6. In a system fordrying a liquid on a liquid-receptive material as set forth in claim 1wherein the spaced electrodes of said antenna have a circular crosssection.
 7. In a system for drying a liquid on a liquid-receptivematerial as set forth in claim 1 wherein the spaced electrodes of saidantenna have a substantially crescent-shaped cross section.
 8. In asystem for drying a liquid on a liquid-receptive material as set forthin claim 1 including means for discharging static electric charge on theliquid-receptive material positioned along the path of travel thereof.9. In a system for drying a liquid on a liquid-receptive material as setforth in claim 8 wherein said means associated with said antenna forsubduing arcing between electrodes comprises: a second plurality ofspaced electrodes, and generating means coupled to said electrodesproducing a current output to generate an electromagnetic field throughwhich tHe liquid-receptive material passes along the path of travelthereof.
 10. In a system for drying a liquid on a liquid-receptivematerial, comprising: a first plurality of electrodes in spaced-apartrelation in an enclosing housing, a second plurality of spacedelectrodes with individual electrodes thereof disposed between adjacentelectrodes of pairs of said first plurality of electrodes inspaced-apart parallel relation thereto, inductance means connectedacross said first and second plurality of electrodes to form a tankcircuit therewith, generating means having a current output directcoupled to said plurality of electrodes in a free-running oscillatorconfiguration to produce an electromagnetic field radiating therefrom tothe liquid-receptive material, dielectric shielding materialssurrounding said electrodes to subdue arcing therebetween, and means formoving the liquid-receptive material through the balancedelectromagnetic field to effect a drying action of the liquid on theliquid-receptive material.
 11. In a system for drying a liquid on aliquid-receptive material as set forth in claim 10 wherein said meansfor moving the material through the balanced electromagnetic fieldincludes gripper bars having opposite ends thereof movable along chainrails, and grounded conductors extended along the chain rails tomaintain said gripper bars at a ground potential.
 12. In a system fordrying a liquid on a liquid-receptive material as set forth in claim 10wherein the electrodes have a substantially crescent-shaped crosssection.
 13. In a system for drying a liquid on a liquid-receptivematerial as set forth in claim 10 wherein said electrodes have asubstantially circular cross section.
 14. In a system for drying aliquid on a liquid-receptive material as set forth in claim 10 whereinthe dielectric shielding material has a low dissipation factor.
 15. In asystem for drying a liquid on a liquid-receptive material as set forthin claim 10 wherein the dielectric shielding material has a highbreakdown voltage.
 16. In a system for drying a liquid on aliquid-receptive material as set forth in claim 10 wherein thedielectric shielding material is formed sheet of tetrafluoroethylenepolymer extending across the front and between the sides of theelectrodes in an undulatory path to provide troughs of shieldingmaterial between adjacent electrodes.
 17. In a system for drying aliquid on a liquid-receptive material as set forth in claim 10 whereinthe electrodes are arranged to form first and second heads, the firsthead and second head being disposed on opposite sides of theliquid-receptive material.
 18. In a system for drying a liquid on aliquid-receptive material as set forth in claim 10 wherein the housingsupporting said electrodes is maintained at a ground potential andconstructed of an electrically conducted material.
 19. In a system fordrying a liquid on a liquid-receptive material as set forth in claim 17including means for urging the liquid-receptive material into slidingcontact with the dielectric shielding material.
 20. In a system fordrying ink on a ink-receptive material as the material moves through aprinting press comprising: a first plurality of shaped electrodes spacedalong and mounted to a first supporting frame, a second plurality ofelectrodes spaced along and mounted to a second supporting frame, saidsecond plurality of electrodes having individual elements thereofdisposed between adjacent electrodes pairs of said first plurality ofelectrodes in a spaced-apart parallel relation thereto, first mountingmeans for supporting the first plurality of spaced electrodes on saidfirst supporting frame, second mounting means for supporting the secondplurality of spaced electrodes on said second supporting frame,inductance means electrically connected between said first plurality andsaid second plurality of electrodes to form a tank circuit therewitH,means for electrically connecting the first supporting frame to ground,and generating means having a current output direct coupled to thesecond supporting frame to form a free-running oscillator with said tankcircuit and for producing an electromagnetic field radiating from saidelectrodes through the ink-receptive material.
 21. In a system fordrying ink on ink-receptive material as set forth in claim 20 includinga static eliminator positioned along the path of the material todischarge static charges on the ink-receptive material prior to thematerial moving through the electromagnetic field produced by said firstand second plurality of electrodes.
 22. In a system for drying ink on anink-receptive material as set forth in claim 20 including meansassociated with the electrodes to prevent ionization of air betweenelectrodes of sufficient magnitude to cause arcing therebetween.
 23. Ina system for drying ink on a ink-receptive material as set forth inclaim 22 wherein said means associated with said electrodes to preventionization of air includes;: a housing extending around the electrodesopposite the path of the moving material, and a blower arranged todirect air through said housing such that ionization of air adjacentsaid electrodes is minimized to prevent arcing.
 24. In a system fordrying ink on an ink-receptive material as set forth in claim 20 whereinsaid electrodes have a substantially crescent-shaped cross section. 25.In a system for drying ink on an ink-receptive material as set forth inclaim 24 wherein the said substantially crescent-shaped cross section ofthe electrodes feathers into a substantially circular cross section atopposite ends of each electrode.
 26. In a system for drying ink on anink-receptive material as set forth in claim 20 including means mountedin spaced-apart relation from the electrodes for directing theink-receptive material into the balanced electromagnetic field.
 27. In asystem for drying ink on an ink-receptive material as set forth in claim26 wherein the means for directing material into the balancedelectromagnetic field is a perforated manifold, and a source ofpressurized air communicating with the manifold to direct air throughthe perforation against the material.
 28. In a system for drying ink onan ink-receptive material as set forth in claim 20 wherein theelectrodes of said first and second plurality are arranged to form firstand second heads, the first head and second head being disposed onopposite sides of the ink-receptive material.